1. Field of the Invention
The present invention relates to a brightness enhancement film and a backlight module having the brightness enhancement film, and more particularly to a brightness enhancement film having first and second micro-reflectors in different average heights and widths and wavy crest lines. The widths of the first and second micro-reflectors vary along with valleys and peaks thereof. The neighboring lines between the first and second micro-reflectors are wavy. This enhances brightness, illuminates evenly, and avoids a moire effect.
2. Description of the Prior Art
A backlight module A of a conventional LCD display, as shown in FIG. 9, comprises a light guide plate A1, a light source A2, a reflector A3, a diffusion film A4, and a brightness enhancement film A5. The light source A2 is disposed at one side of the light guide plate A1 to provide light from a ray entering side A6 to the light guide plate A1 to reflect therein and emit from a ray displaying side A7. The light will then emits through the diffusion film A4 and the brightness enhancement film A5 and reaches to a LCD panel B. The brightness enhancement film A5 can accumulate the light to increase the light as well as to illuminate evenly.
In order to accumulate illumination for a brightness enhancement film to increase the brightness and to illuminate evenly, the surface of the film comprises a number of prisms. As taught in U.S. Pat. No. 5,917,664, a brightness enhancement film has a plurality of linear prisms. The prisms are disposed in pairs, each pair having first and second prisms and each prism has a prism angle and a valley angle. Either the prism angles or the valley angles, but not both, are equal. However, it does not have the function of accumulating light.
Taiwanese Patent No. 1274896 disclosed “an enhancing structure for a light accumulating device”, which comprises a light accumulating device on a baseboard. The light accumulating device has at least a wavy extension surface to enhance light accumulating efficiency. However, this design can not diffuse the light evenly on the display.
Taiwanese Patent No. 1278662 disclosed “an optical film structure”, which comprises micro-prisms formed on an optical film. Each micro-prism has at least two peaks in different heights, preventing the ray from producing interference strips. However, it downgrades the accumulation of light.